The present invention generally relates to clamping devices for connecting discrete elements together, and more particularly, to locking mechanisms which can be used with clamping devices to provide the actuating force needed to move and maintain the clamping devices in a clamped and unclamped position. The present invention also is directed to locking mechanisms which can be associated with camming devices to increase the frictional contact between the cam surface and the contact surface to increase the ability of the camming member to be “locked” in a set position. While the present invention is described with particularity in use within the medical field, particularly to clamping devices used with surgical retraction systems, it should be appreciated that the present invention could be used in non-medical applications where the quick release of clamped elements is desired.
Various surgical retraction systems have been developed over the years for use in surgical operations which require access to internal organs and bone structures. Surgical retraction systems are used to hold back tissue and expose the area in which the surgical operation is to be performed. In many surgical retraction systems, a retractor clamp is utilized to hold the retractor blade used to engage and hold the patient's tissue. The retractor clamp is designed to be mounted on a retractor shaft or rail which is part of a support frame mounted to the operation room table above the patient. The support frame usually includes a number of rails erected above the surgical site which remain stationary throughout the surgical procedure. A number of retractor clamps with retractor blades can be placed along the support frame at appropriate positions to allow the retractor blades to retract the patient's tissue and expose the area for the surgical procedure. Due to factors such as the size and location of the surgical site, along with the variations in patient size, the desired exposure is not always directed to the center of the operation site, which many times require the blade retractors to be re-positioned, elevated or pushed down on the margins of the incision. Accordingly, it is important that the retractor clamp and retractor blade be designed for ease in repositioning into different angular positions as may be needed by the surgical staff in order to properly expose the surgical site for the surgery.
The retractor clamp usually includes an actuation means adapted to apply a compressive force to cause proper clamping engagement of the rod affixed to the retractor blade and the clamp to the rail support. The retractor clamp should be designed such that it is easy to manipulate the actuating means between clamped and unclamped positions and easily re-adjustable to achieve the desire tension necessary to hold back the tissue to expose the area to be surgically treated. It also is important that the retractor clamp itself does not create an obstruction to the surgical site.
Various types of clamping devices have been developed for retraction systems and include those disclosed in U.S. Pat. No. 5,727,899 (Dobrovolny); U.S. Pat. No. 5,792,046 (Dobrovolny); U.S. Pat. No. 5,888,197 (Mulac); U.S. Pat. No. 6,017,008 (Farley); and U.S. Pat. No. 6,277,069 (Gray). These patents generally relate to the basic concept of holding two rod sections in an adjustable and fixable angular relationship relative to one another when placed in a locked position. One of the rod sections is usually a retractor handle that has a retractor blade mounted at one end and is laterally adjustable to engage the tissue at the surgical site. The other rod section is usually the rail of the support frame which allows the retractor blade to be movably placed around the area of the surgical site. Different types of clamps are disclosed in these patents which are designed to engage these rod sections. Many of these devices include a universal joint mechanism which permits quick tightening of the retractor clamp for ease of movement on the rail system along with ease of movement of the retractor blade.
Several of these prior art surgical retraction systems utilize a camming member having a cam face or surface attached to a handle which allows the physician to move the handle in an upward or downward fashion to move the retractor clamp into the clamped or unclamped position. While a camming member is useful in producing the actuating force needed to move the various clamping devices in the clamped position, there is always a possibility that the camming surface can “slip” once placed in the clamped position which can diminish the force acting on the respective clamping devices. If the clamping force should decrease, it is possible for the rod section which holds the retractor blade, for example, to move especially since the retractor blade and retractor rod usually applies tension when retracting the patient's tissue. It should be appreciated that such a reduction in this clamping force is undesirable since the tension applied by the retractor blade to the retracted tissue can also be reduced which can cause the tissue to pull back to its original position.
Therefore, there is a need for the camming device to not only sufficiently develop the actuating or clamping force on the various clamping devices, but to maintain that force without slipping. When a camming surface is utilized, a loss or reduction of frictional contact between the camming surface and the contact surface can result in a loss in the clamping force. Additionally, the resiliency of the clamping device(s) often produces a counteracting force which acts on the camming member to basically urge the camming member back to an unclamped position, where no forces act on the camming member. Frictional contact helps to prevent the camming member from reverting back to the unclamped position; however, many of the prior art systems use an anti-galling washer to reduce friction as the cam face contacts the surface of the anti-galling washer. Reduction in the developed static friction, however, could cause the camming member to “loosen” or “slip” causing a reduction in the clamping force that keeps the components securely clamped together. Accordingly, it is important that the cam surface develop sufficient frictional contact when placed in a clamped or locked position to keep the retractor clamp stable during the entire surgical procedure.
What has been needed is an improved locking mechanism which provides the necessary actuating force to maintain the clamping member(s) in a clamped position without the fear that the locking mechanism will “slip” or “loosen” to cause a loss in the force needed to maintain the clamping member(s) in the clamped condition. Moreover, such a locking mechanism should be easy to deploy and include the ability to be rotated fully with respect to the clamping member(s) to allow greater flexibility in retractor blade placement at the surgical site. Additionally, such a locking mechanism should not obstruct access to the surgical site. The present invention satisfies these and other needs.